Chapter 11: Problem 12
To make a goodness-of-fit test, what should be the minimum expected frequency for each category? What are the alternatives if this condition is not satisfied?
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Chapter 11: Problem 12
To make a goodness-of-fit test, what should be the minimum expected frequency for each category? What are the alternatives if this condition is not satisfied?
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Find the value of \(\chi^{2}\) for 4 degrees of freedom and a. 005 area in the right tail of the chi-square distribution curve b. 05 area in the left tail of the chi-square distribution curve
Four hundred people were selected from each of the four geographic regions (Midwest, Northeast, South, West) of the United States, and they were asked which form of camping they prefer. The choices were pop-up camper/trailer, family style (tenting with sanitary facilities), rustic (tenting, no sanitary facilities), or none. The results of the survey are shown in the following table. \begin{tabular}{l|cccc} \hline & Midwest & Northeast & South & West \\ \hline Camper/trailer & 132 & 129 & 129 & 135 \\ Family style & 180 & 175 & 168 & 146 \\ Rustic & 46 & 50 & 59 & 68 \\ None & 42 & 46 & 44 & 51 \\ \hline \end{tabular} Based on the evidence from these samples, can you conclude that the distributions of favorite forms of camping are different for at least two of the regions? Use \(\alpha=.01\).
Usually people do not like waiting in line a long time for service. A bank manager does not want the variance of the waiting times for her customers to be greater than \(4.0\) square minutes. A random sample of 25 customers taken from this bank gave the variance of the waiting times equal to \(8.3\) square minutes. a. Test at the \(1 \%\) significance level whether the variance of the waiting times for all customers at this bank is greater than \(4.0\) square minutes. Assume that the waiting times for all customers are normally distributed. b. Construct a \(99 \%\) confidence interval for the population variance.
Each of five boxes contains a large (but unknown) number of red and green marbles. You have been asked to find if the proportions of red and green marbles are the same for each of the five boxes. You sample 50 times, with replacement, from each of the five boxes and observe \(20,14,23,30\), and 18 red marbles, respectively. Can you conclude that the five boxes have the same proportions of red and green marbles? Use a \(.05\) level of significance.
Sandpaper is rated by the coarseness of the grit on the paper. Sandpaper that is more coarse will remove material faster. Jobs such as the final sanding of bare wood prior to painting or sanding in between coats of paint require sandpaper that is much finer. A manufacturer of sandpaper rated 220, which is used for the final preparation of bare wood, wants to make sure that the variance of the diameter of the particles in their 220 sandpaper does not exceed \(2.0\) micrometers. Fifty-one randomly selected particles are measured. The variance of the particle diameters is \(2.13\) micrometers. Assume that the distribution of particle diameter is approximately normal. a. Construct the \(95 \%\) confidence intervals for the population variance and standard deviation. b. Test at the \(2.5 \%\) significance level whether the variance of the particle diameters of all particles in 220-rated sandpaper is greater than \(2.0\) micrometers.
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